Device for power generation according to a rankine cycle

ABSTRACT

A device for power generation according to a Rankine cycle, in particular according to an organic Rankine cycle (ORC), comprises a turbine ( 16 ), for expanding a vapour of a working fluid, and at least one heat exchanger ( 18, 20, 22 ), through which the expanded vapour has to flow. The turbine ( 16 ) and the heat exchanger(s) ( 18, 20, 22 ) are contained in a vapour tight container ( 10 ). The turbine ( 16 ) is a radial-outward-flow type turbine having a shaft that is led in a sealed manner out of said container ( 10 ), an axial vapour inlet port arranged opposite the shaft and located inside the container ( 10 ), and a stator exhaust ring with stator exhaust blades defining peripheral vapour exhaust openings for discharging the expanded vapour directly into the vapour tight container ( 10 ), in which the expanded vapour flows through the heat exchanger(s) ( 18, 20, 22 ).

TECHNICAL FIELD

The present invention generally relates to a device for power generationaccording to a Rankine Cycle, in particular to an Organic Rankine Cycle(ORC).

BACKGROUND ART

Due to the general necessity to reduce CO2 emissions and to the loss oftrust in nuclear power plants, devices for producing electricity withlow temperature sources are gaining of importance. Such low temperaturesources include e.g. industrial waste heat, low temperature geothermalheat sources, low temperature biomass energy and low temperature solarenergy, but also novel low temperature heat generators based on chemicalor nuclear reactions.

Such devices generally work according to a so-called Organic RankineCycle (ORC), i.e. a Rankine cycle in which the working fluid is anorganic fluid. The working principle underlying the ORC is basically thesame as that of the classical Rankine cycle in which the working fluidis water. The main difference is that the ORC uses as working fluid anorganic fluid with lower evaporation temperatures than water. It followsthat for the same pressure, the evaporation of the organic fluid takesplace at a lower temperature than the evaporation of water in aclassical Rankine cycle. It follows that the external heat source in anORC may be in a lower temperature range than the external heat source ina Rankine cycle working with water.

A basic ORC comprises following main steps. A condensate pumppressurizes in a liquid phase the condensed organic working fluidcollected at a condenser. The pressurized organic working fluid isheated and evaporated in an evaporator, by heat exchange with anexternal heat source. It will be noted that the evaporation temperaturein an ORC is generally lower than 200° C., most often in the range of100° C. to 160° C., and that the vapour is generally no super-heated.The vapour produced in the evaporator flows through an expansionmachine, wherein its expansion generates a torque for driving anelectrical generator. At the exhaust of the expansion machine, thevapour is condensed in the condenser, which is cooled by heat exchangewith an external cold source. The condensate collected at the condenseris again pressurized in the condensate pump and pumped back into theevaporator.

Today, devices for power generation according to an ORC are commerciallyavailable mainly in a range starting with 0.3 MW electric power output,but there is an increasing need for such devices with a smaller electricpower output too. In particular for the range of 25 kW to 250 kWelectric (corresponding to a thermal recuperation range of about 150 kWto 1.5 MW), there seem to be interesting applications for producingelectricity with low temperature sources using an ORC. However, with adecreasing nominal power of the device used for power generation, theinvestment costs per kW installed strongly increase and the efficiencyof power generation decreases.

It is known that the efficiency of an ORC can be increased by using aso-called regenerator, i.e. a counter-current heat exchanger, which isarranged between the turbine outlet and the condenser inlet. Indeed, ifthe organic fluid is a “dry fluid”, i.e. if it has a positive orisentropic saturation vapour curve, the vapour of the organic fluid hasnot reached the two-phase state when it leaves the turbine. It followsthat the temperature of the expanded vapour is still considerably higherthan the condensing temperature in the condenser. In the regenerator,this temperature difference is used to preheat the pressurizedcondensate before it enters into the evaporator.

If the external heat source is connected into the ORC with a heatcarrier medium, which has to be cooled down in an evaporator working ascounter-current heat exchanger, it is also known to operate an ORC withmore than one evaporator. Each evaporator then works at a differentevaporation pressure, i.e. with a different evaporation temperature, incombination either with a separate expansion machine for each evaporatoror with a single multi-stage expansion machine, in which the vapourproduced in each additional evaporator, is injected into an intermediatestage of the multi-stage expansion machine. Due to the fact that theheat transfer is split between evaporators working at differentevaporation temperatures, one can work with a more important temperaturedifferential on the side of the heat carrier medium, i.e. transform moreheat into power. For power generation in the kW-range, such solutionsare however considered to be a priori too expensive.

ORC systems with more than one evaporator are e.g. described in DE 102007 044 625 A1. According to a first embodiment, the system comprisesseveral separate ORCs, each of these ORCs comprising an evaporator, aturbine, a condenser and a condensate pump. With regard to the heatcarrier fluid, the evaporators are basically connected in series. Witheach evaporator is associated a turbine comprising its own housing witha nozzle system and blade wheels. These turbines are regrouped in pairs,wherein the blade wheels of a turbine pair have a common shaft. Theparallel shafts of two turbine pairs are interconnected by a gear systemto drive an electrical generator. According to a second embodimentdescribed in DE 10 2007 044 625 A1, the system comprises two evaporatorsassociated with a two-stage turbine. This two-stage turbine comprises arotor carrying two axially spaced blade rings, wherein the first bladering has a smaller diameter than the second blade ring. A first steamflow (i.e. high pressure steam produced by a high pressure evaporator)radially enters into the turbine housing through a high pressure inletand flows through a first annular channel radially into a first annularnozzle ring, which deflects the flow in an axial direction into thefirst blade ring, i.e. the blade ring with the smaller diameter. Asecond steam flow (low pressure steam produced by a low pressureevaporator) radially enters into the turbine housing through a lowpressure inlet and flows through a second annular steam channel into asecond nozzle ring, which deflects the flow in an axial direction intothe second blade ring, i.e. the blade ring with the bigger diameter. Thetwo stages are designed so as to achieve the same end pressure at theoutlet of the first and second blade ring, wherein the exhaust streamsare only merged in an outlet diffuser of the turbine. It is obvious thatsuch a turbine has a rather low efficiency, when compared e.g. to atypical induction type turbine, i.e. a multi-stage axial turbine inwhich low pressure steam is induced into the main vapour stream at anintermediate turbine stage and both streams are thereafter commonlyexpanded. However, for power generation with an ORC in the kW-range,known induction type turbines are considered to be too expensive.

The choice of the expansion machine has a major impact on theperformance of the ORC, but also on the costs and therefore on thepay-back time of the power generation device. This is in particular truefor power generation in the kW-range. The use of turbo-machines,generally axial flow turbines, seems to be limited to power ranges above0.3 MW. Below 0.3 MW, displacement type machines, most often derivedfrom existing frigorific compressors, are commonly used. Examples ofdisplacement type machines used in ORCs at lower power ranges are e.g.:reciprocating piston machines, volumetric spiral turbines (also calledscroll turbines) and screw-type machines. All these displacement typemachines have a poor efficiency and generally involve lubricationproblems. Furthermore, displacement type machines often cause problemsdue to a limited tightness.

For making power generation with an ORC in the kW-range a reallyinteresting solution, it would be interesting to implement the ORC in a“black box”, i.e. a preassembled ORC circuit that is integrated in aclosed container and ready to be connected to the heat carrier fluid andthe cooling fluid.

Integrated heat exchanger systems for ORC applications have already beenproposed. EP 1426565 A1 proposes e.g. an integrated thermal exchangergroup for an ORC comprising a regenerator and a condenser, both arrangedin a mainly cylindrical container with a horizontal axis. DE 10 2008 038241 A1 proposes a similar arrangement. These integrated heat exchangersstill require that the turbine and the evaporator are installed asseparate components.

U.S. Pat. No. 5,219,270 describes a recovery assembly for recoveringenergy from a wet oxidation. The assembly comprises a bulky reactionbarrel with rocket nozzles mounted in a vacuum chamber equipped withtubular cooling elements.

GB 1,027,223 describes a multi-stage turbine, wherein a separatecondenser is associated with each turbine stage. The turbine stages areaxially spaced along a common shaft. Each turbine stage discharges theexpanded vapour directly into a chamber containing its separatecondenser. The turbine itself is not further described.

DE 10 2007 037 889 A1 describes a generator, a turbine, an evaporatorand a condenser all mounted in a common housing. The turbine is of amechanically rather complicated and thermodynamically rather inefficientdesign, generating for example high pressure drops in the steam circuit.

SUMMARY OF INVENTION

A device for power generation according to a Rankine cycle (RC), inparticular according to an organic Rankine cycle (ORC), comprises aturbine for expanding a vapour of a working fluid and at least one heatexchanger, such as a regenerator and/or a condenser, through which theexpanded vapour has to flow. In accordance with the invention, thedevice further comprises a vapour tight container containing the turbineand the at least one heat exchanger. The turbine is aradial-outward-flow type turbine having: a shaft that is led in a sealedmanner out of the container; an axial vapour inlet port arrangedopposite the shaft so as to be located inside the container; and astator exhaust ring with stator exhaust blades defining peripheralvapour exhaust openings for discharging the expanded vapour directlyinto the vapour tight container, in which the expanded vapour flowsthrough the at least one heat exchanger. It will be appreciated that theinvention combines in a very efficient way, a very compact, but veryefficient radial-outward-flow type turbine and at least one heatexchanger, which is to be traversed by the vapour expanded in theturbine, in a common vapour tight containment. The axial vapour inletport is hereby arranged opposite the shaft and located inside thecontainer, where it can be very easily connected to an internal vapourgenerator. The direct peripheral expanded vapour discharge through thestator exhaust ring with its stator exhaust blades into the commoncontainer substantially reduces pressure losses between the turbine andthe at least one heat exchanger. The common container also reduces therisk of (organic) vapour losses to the atmosphere. The fact that aseparate, vapour tight turbine housing is not necessary, reduces thecosts and makes an up-sizing or down-sizing of the turbine much easier.

In a preferred embodiment, the container has the form of a verticalcylinder with a top end and a bottom end. In this case, the turbine isadvantageously centred in the top end of the container, and the at leastone heat exchanger is located below the turbine. It will be appreciatedthat this design provides ideal flow conditions for the expanded vapourbetween the exhaust of the turbine and the at least one heat exchanger.

A preferred embodiment of the turbine is a radial-outward-flow typemulti-stage turbine with vapour induction in at least one intermediarystage. In this embodiment, an annular vapour inlet port advantageouslysurrounds the axial vapour inlet port, and is arranged in the turbine soas to annularly induce, in an intermediary stage of the turbine, avapour stream from a second evaporator into an already partiallyexpanded vapour stream from a first evaporator. It will be appreciatedthat the proposed radial-outward-flow type, multi-stage turbine can bevery easily configured as an induction type turbine, wherein themanufacturing costs for the induction type turbine are not much higherthan for a turbine with a single vapour inlet.

In a preferred embodiment, the device further includes a firstevaporator and, optionally, a second evaporator. The first evaporatorand, if present, the second evaporator are advantageously arranged inthe container, axially below the axial vapour inlet port of the turbine.The at least one heat exchanger is then advantageously arrangedannularly around the first evaporator and, if the second evaporator ispresent, annularly around the first and second evaporator. With such anarrangement, the device gets particularly compact. Furthermore, theintergration of the evaporator(s) into a common container with theturbine and at least one heat exchanger located downstream of theturbine, further reduces the risk of (organic) vapour losses to theatmosphere. Arranging the the evaporator(s) axially below the axialvapour inlet port of the turbine also allows to reduce pressure and heatlosses between the evaporator(s) and the turbine. It remains to be notedthat the evaporator that is arranged in the common container may also bea vapour generator comprising an internal heat source, e.g. a novel typeof low temperature heat source, which is based on chemical or nuclearreactions.

A preferred embodiment of the device further comprises a first vapourdrum that is located in axial extension of the axial vapour inlet portand directly connected to the latter without any intermediate piping. Ifthe turbine is a multi-stage turbine with vapour induction in anintermediary stage, this embodiment further comprises a second vapourdrum that is located in axial extension of the annular vapour inlet portand directly connected to the latter without any intermediate piping. Inthis case, the second vapour drum is a compartment inside the firstvapour drum, or the first vapour drum is a compartment inside the secondvapour drum. In such an embodiment, the axial vapour inlet port isadvantageously formed by a first tubular vapour inlet connection, whichis engaged in a sliding and sealed manner by the first vapour drum; andthe annular vapour inlet port, if present, is advantageously formed by asecond tubular vapour inlet connection surrounding the first tubularvapour inlet connection, wherein the second tubular vapour inletconnection is advantageously engaged in a sliding and sealed manner bythe second vapour drum. If the first evaporator and second evaporatorare—in this preferred embodiment—arranged axially below the axial vapourinlet port of the turbine, the first vapour drum and/or the secondvapour drum are advantageously supported by the first evaporator and/orsecond evaporator or by a support structure associated with the firstevaporator and/or second evaporator. Such combined low and high pressurevapour drums, which are connected without any intermediate piping and,preferably, with sliding connections to the turbine vapour inlets,reduce pressure losses at the vapour inlet(s) of the turbine, allow toeasily achieve a superheating of the low pressure vapour by the highpressure vapour, thereby increasing efficiency of the Rankine cycle,make the device more compact, facilitate its assembling and reduce itscosts.

In a preferred embodiment, the at least one heat exchanger includes afirst regenerator that is arranged in the container so that the exhaustvapour of the turbine flows directly through it; this first regeneratorbeing connected to a fluid inlet port of a first evaporator, so as toreheat the fluid with heat extracted from the exhaust vapour flowingthrough the first regenerator. The at least one heat exchanger mayfurther include a second regenerator that is arranged in the containerso that the vapour having crossed the first regenerator flows throughit; this second regenerator being connected to a fluid inlet port of asecond evaporator, so as to reheat the fluid with heat extracted fromthe vapour flowing through the second regenerator. Such a double-stageregeneration allows to significantly increase the efficiency of theRankine cycle.

The at least one heat exchanger may also include a condenser in whichthe expanded vapour is condensed, wherein, if present, the firstregenerator, the second generator and the condenser are arranged belowthe turbine, vertically one above the other. This configuration is notonly very compact. It also provides nearly ideal flow conditions for thevapour between the exhaust of the turbine, the regenerators and thecondenser.

In a preferred embodiment, the device further includes a firstevaporator connected to an axial vapour inlet port of the turbine, asecond evaporator working at a lower evaporation pressure than the firstevaporator and connected to an annular vapour inlet port of the turbinefor inducing lower pressure vapour into an intermediary stage of theturbine; for the first evaporator, a first heat carrier fluid inlet portand a first heat carrier fluid outlet port; for the second evaporator, asecond heat carrier fluid inlet port and a second heat carrier fluidoutlet port; a connection pipe connecting the first heat carrier fluidoutlet port to the second heat carrier fluid inlet port; and optionally,a bypass-valve connected between the second heat carrier fluid inletport and the second heat carrier fluid outlet port, for adjusting theflow rate of the heat carrier fluid in the second evaporator. Such aconfiguration allows to further optimize the RC, and in particular theORC.

In a preferred embodiment, the at least one heat exchanger includes acondenser, and a condensate collector is arranged under the condenser inthe container. In this embodiment: a condensate outlet port isadvantageously connected to the condensate collector; a first condensateinlet is advantageously connected either directly or through a firstregenerator to a first evaporator; a second condensate inlet isadvantageously connected, either directly or through a secondregenerator, to a second evaporator; and a condensate pump isadvantageously connected with its suction side to the condensatecollector, and with its pressure side via a first valve to the firstcondensate inlet and via a second valve to the second condensate inlet.Such a configuration allows to further optimize the RC, and inparticular the ORC.

In an alternative embodiment, the device includes an air-cooledcondenser arranged outside the container connected to the container bymeans of a large diameter vapour pipe. The at least one heat exchangerthen includes at least one regenerator arranged in the container so thatthe expanded vapour flows through it before being channelled through thelarge diameter pipe into the air-cooled condenser. It will beappreciated that even with an external air-cooled condenser, the devicecan remain very compact.

A preferred embodiment of the turbine comprises: a substantiallyplate-shaped first turbine housing part including the axial vapour inletport; a set of stator rings with stator blades, the stator rings havingincreasing diameters and being preferably fixed with screws onto thefirst turbine housing part; a stator exhaust ring with stator exhaustblades, the stator exhaust ring radially surrounding the stator ringwith the biggest diameter and being preferably fixed with screws ontothe first turbine housing part, the stator exhaust blades defining thevapour exhaust openings for discharging the expanded vapour into thecontainer; a substantially plate-shaped second turbine housing partincluding a shaft outlet neck; the second turbine housing part beingpreferably fixed with screws onto the stator exhaust ring; a turbineshaft rotatably supported within the shaft outlet neck; a rotor disksupported in a cantilever manner by the turbine shaft between the firstturbine housing part and the second turbine housing part; for eachstator ring, a rotor ring with rotor blades, the rotor ring radiallysurrounding the corresponding stator ring and being fixed with screwsonto the rotor disk. A main advantage of such a turbine design is thatthe turbine may be easily up-sized or down-sized, and that it may beeasily fine-tuned to specific working parameters. Hence, an optimalturbine efficiency may nearly always be warranted.

The turbine advantageously includes an annular vapour inlet port formedin the first turbine housing part as a ring-zone with through-holes, thering-zone separating a first ring-shaped flange, which supports a firstset of stator rings, from a second ring-shaped flange, which supports asecond set of stator rings. A vapour induction port may thus be added tothe turbine with very simple means and at very low costs.

In a preferred embodiment, the turbine is an induction turbinecomprising: a first turbine housing part including the axial vapourinlet port; a set of stator rings with stator blades supported by thefirst turbine housing part; a turbine shaft supporting in a cantilevermanner a rotor disk; for each stator ring, a rotor ring with rotorblades, the rotor ring radially surrounding the corresponding statorring and being supported by the rotor disk; an annular vapour inlet portformed in the first turbine housing part as a ring-zone withthrough-holes. These through-holes advantageously open onto an outer rimof one of the rotor rings, this outer rim having a width decreasingtowards its periphery, and forming an annular, preferably concave,surface, which defines with an annular, preferably convex, surface onthe next stator ring, a ring-shaped converging nozzle, for annularlyinducing, into the next stator ring, a vapour stream from thethrough-holes into a vapour stream flowing through the preceding rotorring. Thus, vapour induction is fluidically optimized at relatively lowcosts.

In a preferred embodiment of the turbine, the first turbine housing partsupports an end-cap, which forms a vapour inlet deflection surfaceopposite the axial vapour inlet port; this vapour inlet deflectionsurface being a revolution surface centred on the central axis of theturbine; wherein a first stator ring is integrated into the end-cap.

In a preferred embodiment, the second turbine housing part is mounted ina sealed manner in an opening of the container, so that a shaft outletneck of the second turbine housing part is located outside thecontainer. In this embodiment, the turbine adavantageously furtherincludes: rolling contact bearings in the shaft outlet neck forsupporting and locating the turbine shaft therein; and a shaft sealingdevice located adjacent to the rolling contact bearings, so that therolling contact bearings are sealed from the vapour in the turbine.Hence, the shaft bearings may be rather standard rolling contactbearings, which are easily accessible outside the common container formonitoring and maintenance purposes.

BRIEF DESCRIPTION OF DRAWINGS

The afore-described and other features, aspects and advantages of theinvention will be better understood with regard to the followingdescription of an embodiment of the invention and upon reference to theattached drawings, wherein:

FIG. 1: is a block diagram schematically illustrating how differentcomponents of a preferred device for power generation according to animproved organic Rankine cycle (ORC) are interconnected;

FIG. 2: is a schematic sectional view of a multi-stage turbine, in whichlow pressure vapour is induced at a low pressure turbine stage, thesection plane containing the central axis of the turbine;

FIG. 3: is an enlarged detail of FIG. 2;

FIG. 4: is a schematic sectional view of a turbine as shown in FIG. 2,the section plane being this time perpendicular to the central axis ofthe turbine;

FIG. 5: is a schematic sectional view of the turbine as in FIG. 2,further schematically showing a first arrangement of a high pressurevapour drum and a low pressure vapour drum directly connected to theturbine;

FIG. 6: is a schematic sectional view as in FIG. 5, showing a slightlymodified embodiment;

FIG. 7: is a schematic sectional view as in FIG. 5, showing a furtherpossibility how to connect the high pressure vapour drum and the lowpressure vapour drum to the turbine;

FIG. 8: is a schematic sectional view as in FIG. 5, showing anadditional possibility how to connect the high pressure vapour drum andthe low pressure vapour drum to the turbine;

FIG. 9: is a schematic sectional view of a device in accordance with theinvention, the section plane being a vertical plane; and

FIG. 10: is a schematic sectional view of as indicated by line 9-9′ inFIG. 9;

FIG. 9: is a schematic sectional view of a device in accordance with theinvention, which is equipped with an air cooled condenser.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

It will be understood that the following description and the drawings towhich it refers describe by way of example preferred embodiments of theclaimed subject matter for illustration purposes. The description anddrawings shall not further limit the scope, nature or spirit of theclaimed subject matter.

FIG. 1 is a block diagram schematically illustrating how differentcomponents of device for power generation according to an improvedOrganic Rankine Cycle (ORC) are interconnected. This device comprisesfollowing main components arranged within a closed vapour tightcontainer 10: a first or high pressure evaporator 12, a second or lowpressure evaporator 14; a turbine 16; a condenser 18 and tworegenerators 20, 22. It further comprises a condensate pump 24 and anelectrical generator 26, which are preferably arranged outside of thecontainer 10.

The preferred device comprises moreover following fluid inlet and outletports:

-   -   a first heat carrier fluid inlet port 30, respectively outlet        port 30′, connected to the heat carrier fluid inlet,        respectively the heat carrier fluid outlet of the first        evaporator 12;    -   a second heat carrier fluid inlet port 32, respectively outlet        port 32′, connected to the heat carrier fluid inlet,        respectively the heat carrier fluid outlet of the second        evaporator 14;    -   a cooling fluid inlet port 34, respectively outlet port 34′        connected to the cooling fluid inlet, respectively the cooling        fluid outlet of the condenser 18;    -   a condensate outlet port 36;    -   a first condensate inlet port 38; and    -   a second condensate inlet port 40.

Reference number 42 identifies an external heat transfer circuit,associated e.g. with a low temperature external heat source. In thisexternal heat transfer circuit 42 circulates a heat carrier fluid, suchas a heat-transfer-oil, which transports the heat energy to betransformed by the ORC in mechanical energy. The heat carrier fluidenters through the first heat carrier fluid inlet port 30 into the firstevaporator 12, traverses the latter, thereby heating and evaporating anorganic working fluid flowing through the first evaporator 12.Thereafter, the heat carrier fluid leaves the container 10 through thefirst heat carrier fluid outlet port 30′, to be channelled through anexternal connection conduit 44 to the second heat carrier fluid inletport 32. Through this second heat carrier fluid inlet port 32, the heatcarrier fluid enters into the second evaporator 14, traverses thelatter, thereby heating and evaporating the organic working fluidflowing through the second evaporator 14. Thereafter, the heat carrierfluid definitively leaves the container 10 through the second heatcarrier fluid outlet port 32′.

As an alternative to the external connection conduit 44, it is possibleto foresee an internal connection conduit (not shown) located within thecontainer 10, which would eliminate the first heat carrier fluid outletport 30′ and the second heat carrier fluid inlet port 32. However, thesolution with the external first heat carrier fluid outlet port 30′ andthe second heat carrier fluid inlet port 32 warrants a greaterflexibility. Thus, instead of connecting the first and second evaporator12, 14 in series with regard to the heat carrier fluid, it is e.g.possible to connect the first evaporator 12 to a first heat transfercircuit (not shown), and the second evaporator 14 to a separate secondheat transfer circuit (not shown).

In the embodiment shown in FIG. 1, a bypass-valve 45 is moreoverconnected between the second heat carrier fluid inlet and outlet ports32, 32′. This bypass-valve 45 allows limiting the flow of heat carrierfluid through the second evaporator 14, thereby limiting the At of theheat carrier fluid between the ports 30 and 32′. The more thebypass-valve 45 is opened, the higher the outlet temperature of the heatcarrier fluid at port 32′ and, consequently, the lower the At of theheat carrier fluid between the ports 30 and 32′ will be.

The organic fluid vapour produced in the first evaporator 12, calledhereinafter high pressure vapour, is channelled into a high pressurevapour drum 46, which is directly, i.e. without any intermediate piping,connected to a high pressure inlet of the turbine 16. The organic vapourproduced in the second evaporator 14, which has a lower pressure thanthe organic vapour produced in the first evaporator 12 and is thereforecalled low pressure vapour, is channelled into a low pressure vapourdrum 48, which is directly, i.e. without any intermediate piping,connected to a low pressure inlet of the turbine 16. In the turbine 16,both vapour streams are expanded to generate a torque for driving thegenerator 26 coupled to the turbine 16.

To protect the turbine 16 against damage by organic fluid dropletsimpacting onto the turbine blades, the ORC cycle is generally designedso that the vapour at the turbine exhaust has not yet reached atwo-phase state (to achieve this aim the organic fluid should preferablybe a “dry” ORC working fluid, i.e. it should have a positive orisentropic saturation vapour curve). It follows that the temperature ofthe vapour at the outlet of the turbine 16 is still much higher than thecondensing temperature in the condenser 18. In the two regenerators 20and 22, this temperature difference is efficiently used to preheat thecondensate before it enters into evaporator 12 or 14. More particularly,the first regenerator 20, which is heated directly with the exhaustvapour of the turbine 16, preheats the condensate stream pumped throughthe first evaporator 12, which works at a higher pressure andconsequently also with a higher evaporating temperature than the secondevaporator 14. The second regenerator 22, which is heated with thevapour already cooled down in the first regenerator 20, preheats thecondensate stream pumped through the second evaporator 14, which worksat a lower evaporating temperature. It will be appreciated that thistwo-stage regeneration allows a more efficient heat exchange in theregenerators 20, 22 and the evaporators 12, 14 than a single-stageregeneration.

In the condenser 18, the organic working fluid is condensed by means ofan external cooling circuit 50 connected to the cooling fluid inlet port34 and outlet port 34′ of the condenser 18. Such an external coolingcircuit 50 may e.g. comprise a dry or a wet cooling tower (not shown).

The condensate pump 24 pressurizes the condensed organic working fluidcollected at the condenser 18 and pumps it through the regenerators 20,22 to the two evaporators 12, 14. More particularly, at the outlet ofthe condensate pump 24, the pressurized condensate is split in twoseparate condensate streams. A first condensate stream is pumped througha first valve 52, which is connected to the first condensate inlet port38. This first condensate stream flows through the first regenerator 20,wherein it is pre-heated by the exhaust vapour of the turbine 16, intothe first evaporator 12. A second condensate stream is pumped through asecond valve 54, which is connected the second condensate inlet port 40.This second condensate stream flows through the second regenerator 22,wherein it is pre-heated by the expanded vapour, into the secondevaporator 14. The first and second valve 52, 54 allow to adjust thepressures in the evaporator 12 and 14 independently from one another.Alternatively, two separate condensate pumps can be used, one forpumping the first condensate flow through the first regenerator 20 intothe first evaporator 12, and the other for pumping the second condensateflow through the second regenerator 22 into the second evaporator 14.

It will be understood that the pressures and temperatures depend on thecharacteristics of the heat carrier circuit 42, on the type of organicworking fluid used in the ORC, on the characteristics of the availablecooling circuit 50, and on the dimensioning of the heat exchangers 12,14, 18, 20, 22, the turbine 16, and the condensate pump 24. Followingvalues are listed for illustrating the ORC presented with a realisticexample:

Heat Carrier Fluid in the External Heat Transfer Circuit 42:

Type: customary heat-transfer-oilInlet temperature at 30: 180° C.Outlet temperature at 32′: 75° C.

Organic Working Fluid:

Type: Solkane® 365mfc produced by SOLVAYFirst evaporation temperature: 158° C. (20 bar)Second evaporation temperature: 86° C. (4.5 bar)Vapour outlet temperature of the turbine 16: 74° C.Vapour outlet temperature of the first regenerator 20: 60° C.Vapour outlet temperature of the second regenerator 22: 45° C.Condensate temperature at the outlet of condenser 18: 35° C.Condensate temperature at the inlet of first evaporator 12: 68° C.Condensate temperature at the inlet of second evaporator 14: 55° C.The efficiency of this two-stage ORC is about 15% for a Δt of 100° C.,but about 11% of the available energy in the heat carrier fluid isconverted into mechanical energy. Without the low pressure circuit (i.e.without the second evaporator 14, the second regenerator 22, the lowpressure vapour drum 48 and the low pressure vapour inlet of the turbine16), the efficiency of the single stage ORC would be about 21%, but onlyabout 7% of the available energy in the heat carrier fluid would beconverted into mechanical energy.

Typical temperature ranges for the heat carrier fluid are e.g.:

Inlet temperature of the heat carrier fluid: 140° C. to 350° C.Outlet temperature of the heat carrier fluid: 66 to 150° C.

In an alternative embodiment (not shown), the circuit of FIG. 1 onlycomprises the first regenerator 20, i.e. the second condensate inletport 40 is directly connected to the second evaporator 14, withoutpassing by a regenerator. In certain cases it may moreover beinteresting to work without any regenerator. In this case, the firstcondensate inlet port 40 is directly connected to the first evaporator14, and the second condensate inlet port 40 is directly connected to thesecond evaporator 14, without passing by a regenerator.

In a further embodiment (not shown), the circuit comprises in additionto the high pressure evaporator 12 more than one low pressureevaporator, each of these low pressure evaporators supplying the turbine16 with vapour at a different intermediate pressure, which is inducedinto the turbine at a stage in which the pressure of the expanded vapouris about equal to the pressure of the induced vapour. In thismulti-induction embodiment, a regenerator can be associated with eachevaporator or only with one or more selected evaporators.

Finally, if the possible or desired At for the heat carrier fluid israther small, it is also possible to work solely with the high pressureevaporator 12 and a turbine without low pressure inlet.

FIG. 2 is a schematic cross-section through an embodiment of the turbine16 that is particularly suited for being used in an ORC as describedabove. It will first be noted that the turbine 16 is a multi-stage (herea three-stage) radial-outward-flow type turbine, i.e. the vapour axiallyenters into the turbine 16 and then flows in a radial direction outwardthrough the different stages of the turbine 16, which are substantiallyconcentric. The turbine is furthermore of the induction type, i.e. asecondary flow of low pressure vapour is induced at a low pressure stageinto the turbine 16. Finally, the turbine is of the impulse type, i.e.the vapour is mainly expanded as it passes through the stator of theturbine 16.

As best seen in the cross-section of FIG. 4, each of the three turbinestages comprises a stator ring 56 ₁, 56 ₂, 56 ₃, with increasingdiameter and curved stator blades 58 ₁, 58 ₂, 58 ₃, and a rotor ring 60₁, 60 ₂, 60 ₃, with increasing diameter and curved rotor blades 62 ₁, 62₂, 62 ₃. The inlet stator ring 56 ₁ and the first rotor ring 60 ₁ formthe first stage of the turbine 16. The second stator ring 56 ₂ and thesecond rotor ring 60 ₂ form the second stage of the turbine 16. Thethird stator ring 56 ₃ and the third rotor ring 60 ₃ form the thirdstage of the turbine 16. A fourth ring 56 ₄ surrounds the third or laststage of the turbine 16, to form a stator exhaust ring 56 ₄, with statorexhaust blades 58 ₄. It will of course be understood that the turbine 16may also be designed with 4 stages or more, by adding one or more pairsof stator and rotor rings.

Referring now to FIG. 2, it will be noted that the rotor rings 60 ₁, 60₂, 60 ₃ are supported by a rotor disk 64, which is fixed to a free endof a turbine shaft 66. The turbine shaft 66 with the rotor disk 64 isrotatably supported in a cantilever fashion in a shaft outlet neck 72 bymeans of a bearing arrangement, preferably built up with rolling contactbearings. Reference number 68 points to a schematic representation ofsuch a rolling contact bearing. Reference number 70 identifies aschematic representation of a sealing device, which seals the shaft 66in the shaft outlet neck 72, between the rotor disk 64 and the bearingarrangement.

Reference number 74 identifies the central axis of the turbine shaft 66,which is also the central axis of all rotor rings 60 ₁, 60 ₂, 60 ₃ (andof all stator rings 56 ₁, 56 ₂, 56 ₃, 56 ₄), since all these rings arecoaxial with the turbine shaft 66. It will be noted that the rotor disk64 is axially secured to the turbine shaft 66, e.g. by means of a nut 75or a screw (not shown), and that the torque is transmitted from therotor disk 64 to the turbine shaft 66 by means of a form-fit or keyedassembly (not shown). The rotor rings 60 ₁, 60 ₂, 60 ₃ are fixed withscrews 76 to the rotor disk 64, so that they are easily exchangeable.

Still referring to FIG. 2, the stator rings 56 ₁, 56 ₂, 56 ₃ are fixedwith screws 78 to a plate-shaped first turbine housing part 80. Thisfirst turbine housing part 80 comprises a first and a second tubularvapour inlet connection 82, 84, a first and a second ring-shaped flange88, 90 and a perforated ring zone 92. The first tubular vapour inletconnection 82 is centred on the central axis 74 of the turbine 16. Thesecond tubular vapour inlet connection 84 surrounds the first tubularvapour inlet connection 82, so as to define with the latter an annularspace 86, wherein the perforated ring zone 92 is contained in thisannular space 86. The first ring-shaped flange 88 forms a shoulderaround the first tubular vapour inlet connection 82. The secondring-shaped flange 90 forms a shoulder around the second tubular vapourinlet connection 84. The perforated ring zone 92 joins the first flange88 and the second ring-shaped flange 90 and is provided withthrough-holes 94.

It will be noted that instead of being integral with the first turbinehousing part 80, the first and/or second tubular vapour inlet connection82, 84 could also be flanged to the first turbine housing part 80. Inthis case, the first turbine housing part 80 mainly consists of thefirst ring-shaped flange 88, the second ring-shaped flange 90 and theperforated ring zone 92, which joins the first and the secondring-shaped flange 88, 90. In this embodiment, the first ring-shapedflange 88 advantageously comprises a first connection means for flanginga removable first vapour inlet connection thereto, and the secondring-shaped flange 90 advantageously comprises a second connection meansfor flanging a removable second vapour inlet connection thereto (notshown in the drawings).

The first ring-shaped flange 88 supports the first and the second statorring 56 ₁, 56 ₂. The first stator ring 56 ₁ is advantageously part of anend-cap 96, which forms a vapour inlet deflection surface 98 at the endof the first tubular vapour inlet connection 82. This vapour inletdeflection surface 98 is a revolution surface centred on the centralaxis 74 of the turbine 16, so as to annularly deflect the axial vapourstream in the first tubular vapour inlet connection 82 by 90° into thefirst stator ring 56 ₁.

The second ring-shaped flange 90 supports the third stator ring 56 ₃, aswell as the exhaust stator ring 56 ₄. By means of the exhaust statorring 56 ₄, the first turbine housing part 80 is fixed to a plate-shapedsecond turbine housing part 100. The rotor disk 64 with the rotor rings60 ₁, 60 ₂, 60 ₃ is hereby located axially between the first housingpart 80 and the second housing part 100. In the radial direction, thefirst rotor ring 60 ₁ is located between the first and the second statorring 56 ₁ and 56 ₂; the second rotor ring 60 ₂ is located between thesecond and the third stator ring 56 ₂ and 56 ₃; and the third rotor ring60 ₃ is located between the third stator ring 56 ₃ and the exhauststator ring 56 ₄. It will be appreciated that—with this sandwichdesign—the height of the stator blades 58 ₁, 58 ₂, 58 ₃ and rotor blades62 ₁, 62 ₂, 62 ₃ can be modified, by simply exchanging the removablestator rings 56 and rotor rings 60. Consequently, with one size for thefirst and second turbine housing part 80 and 100, the rotor disk 64 andthe turbine shaft 66, one may already cover a large range of pressuresand flow rates. Thus, it will be e.g. be possible to cover the electricpower range of 25 kW to 100 kW with one unique size for the first andsecond turbine housing part 80 and 100, the rotor disk 64 and theturbine shaft 66. In most cases it will even not be necessary to changethe form of the rotor and stator blades 58, 62. A broad electric powerrange may be covered by simply changing the height of the rotor andstator blades 58, 62, all other geometric characteristics of the rotorand stator rings 56, 60 and blades 58, 62 remaining unchanged.Furthermore, if the available heat energy increases or decreases duringlifetime of the turbine, the latter may be easily reconfigured for thenew operating conditions by simply exchanging its rotor and stator rings56, 60.

As is best seen in FIG. 3, each of the three stator rings 56 ₁, 56 ₂, 56₃ includes at its base an annular shoulder 102 ₁, 102 ₂, 102 ₃, whichforms a labyrinth joint 10 ₆ with an opposite grooved surface located onan annular outer rim 104 ₁, 104 ₂, 104 ₃ of the corresponding rotor ring60 ₁, 60 ₂, 60 ₃. Similarly, each of the first two rotor rings 60 ₁, 60₂ includes at its base an annular shoulder 108 ₁, 108 ₂, which forms alabyrinth joint 112 with an opposite grooved surface located on anannular outer rim 110 ₂, 110 ₃ of the corresponding stator ring 56 ₂, 56₃. Thus, vapour tightness in the radial direction between the rotatingand stationary parts is solely achieved by easily machinable surfaces onthe removable stator rings 56 ₁, 56 ₂, 56 ₃ and rotor rings 60 ₁, 60 ₂,and necessitates neither complicated machining on the turbine housingparts 80, 100 or the rotor disk 64, nor separate sealing elements.Furthermore, if the removable rotor and stator rings 56, 60 arereplaced, all sealing surfaces in the turbine are replaced too.Alternatively, the removable stator rings 56 ₁, 56 ₂, 56 ₃ and rotorrings 60 ₁, 60 ₂, may be designed without the aforementioned annularshoulder, wherein the outer rims 104 ₁, 104 ₂, 104 ₃ of the rotor rings60 ₁, 60 ₂, 60 ₃ and the outer rims 110 ₂, 110 ₃ of the stator rings 56₂, 56 ₃ cooperate directly with corresponding annular surfaces on thehousing part 80 and the rotor disk 64 to form labyrinth joints.

It will further be noted that the annular shoulder 102 ₂ of the secondstator ring 56 ₂ is smaller than the other two annular shoulders 102 ₁,102 ₃, thereby leaving uncovered the through-holes 94 in the perforatedring zone 92 of the first turbine housing part 80. The width of theannular outer rim 104 ₂ of the second rotor ring 60 ₂, which is locatedjust behind the perforated ring zone 92, decreases towards itsperiphery, so as to define with the opposite surface of the third statorring 56 ₃ a ring-shaped converging nozzle 114, which is delimited, onone side, by an annular concave surface 116 defined by the second rotorring 60 ₂ and, on the other side, by an annular convex surface 118defined by the third stator ring 56 ₃. This ring-shaped nozzle 114deflects the low pressure vapour stream, which flows from the annularspace 86 in an axial direction through the through-holes 94, by an angleof 90° into the third stator ring 56 ₃. In this third stator ring 56 ₃,this low pressure vapour stream is induced into the main vapour streamthat has already been expanded in the first and second stage of theturbine 16, so that both vapour streams have substantially the samepressure when they merge in the third stator ring 56 ₃.

Referring simultaneously to FIG. 2 and FIG. 4, it will be noted that theexpansion of the vapour in the second stator ring 56 ₂ and the thirdstator ring 56 ₃ is mainly achieved by increasing the height of thestator blades 58 in the radial direction (i.e. the height of theseblades at the outlet is considerably higher than their height at theinlet of the stator ring). Thus, the expansion of the vapour in thesestator rings 56 ₂ and 56 ₃ is mainly determined by the increasing heightof their blades. Consequently, for adapting the turbine to a differentvapour throughput or a different inlet pressure in the turbine 16, itwill not be necessary to entirely change the geometry of the rotor orstator blades 58, 62. It will most often simply be sufficient to changethe height of the rotor and stator blades 58, 62, all other geometriccharacteristics of the rotor and stator rings 56, 60 and blades 58, 62remaining basically unchanged.

It will be appreciated that the turbine as described hereinbefore mayachieve an isentropic efficiency as high as 90%. Its rotation speed willpreferably be limited to 18,000 rpm, so to be capable of working withrolling contact bearings and common shaft sealing devices.

FIG. 5 schematically shows a first arrangement of the high pressurevapour drum 46 and the low pressure vapour drum 48, both directlylocated under the turbine 16 and directly connected to latter withoutany intermediate piping. The high pressure vapour drum 46 is acylindrical vessel directly flanged to the first turbine housing part80. The low pressure vapour drum 48 forms an annular compartment withinthe high pressure vapour drum 46. This annular compartment is outwardlydelimited by a cylindrical external wall 120 of the high pressure vapourdrum 46 and inwardly delimited by a cylindrical internal wall 122. Thiscylindrical internal wall 122 engages the first tubular vapour inletconnection 82 of the turbine 16 in a sealed fit, wherein this sealed fitshall however be designed (e.g. with O-rings) to allow relative axialmovement of the cylindrical internal wall 122 and the first tubularvapour inlet connection 82. The high pressure vapour flows through theaxial passage delimited by the cylindrical internal wall 122 into thefirst tubular vapour inlet connection 82 of the turbine. The lowpressure vapour flows directly from the annular low pressure vapour drum48 into the annular space 86 delimited between the first tubular vapourinlet connection 82 and the second tubular vapour inlet connection 84 ofthe turbine. Reference number 124 points to a high pressure vapour inletpipe connected laterally to the high pressure vapour drum 46, whereasreference number 126 points to a low pressure vapour inlet pipeconnected laterally to the low pressure vapour drum 48.

The arrangement of FIG. 6 distinguishes over the arrangement of FIG. 5mainly in that the low pressure vapour inlet pipe 126′ traverses thehigh pressure vapour drum 46 to leave the latter through its bottomwall. This design necessitates that the low pressure vapour inlet pipe126 and the high pressure vapour drum 46 may freely expand relative toone another. This can e.g. be achieved by connecting the low pressurevapour inlet pipe 126 by means of a bellow expansion joint (not shown)to the closed end of the high pressure vapour drum 46.

FIG. 7 shows a further arrangement of the high pressure vapour drum 46and the low pressure vapour drum 48 connected to the turbine 16. The lowpressure vapour drum 48 is a cylindrical vessel flanged to the firstturbine housing part 80. The high pressure vapour drum 46 forms acylindrical compartment within the low pressure vapour drum 48,separated from the outer wall of the latter by an annular space 130. Itis vertically supported by a support flange 132, which is welded intothe low pressure vapour drum 48. Through-openings 134 in the supportflange 132 allow the intermediate pressure vapour to pass from an inletcompartment 136 of the low pressure vapour drum 48 into the annularspace 130. The high pressure vapour drum 46 engages the first tubularvapour inlet connection 82 of the turbine 16 in a sealed way, whereinthis sealed fit shall however be designed (e.g. with O-rings) to allowrelative axial movement of the high pressure vapour drum 46 and thefirst tubular vapour inlet connection 82. Similarly as for the pipe 126′in the embodiment of FIG. 6, the passage of the pipe 124 through thebottom wall of the low pressure vapour drum 48 is designed for allowinga relative axial expansion of both components.

It will be noted that in FIGS. 5, 6 and 7, the outer vessel is flangedto the first turbine housing part 80 of the turbine 16, and mustconsequently be able to axially expand away from the turbine 16. In FIG.8, the outer vessel 140 is no longer flanged to the first turbinehousing part 80 of the turbine 16. It simply engages the second tubularvapour inlet connection 84 of the turbine 16 in a sealed way, whereinthis sealed fit is designed (e.g. with O-rings) to allow a relativeaxial movement of the outer vessel 140 and the second tubular vapourinlet connection 84. In this embodiment, the outer vessel 140 (which maybe the high pressure vapour drum 46 as in FIG. 5 or 6, or the lowpressure vapour drum 48 as in FIG. 7) can be vertically supported by aseparate vertical support means 142. Thus, the outer vessel 140 may e.g.be directly supported on the first or second evaporator 12, 14, when thelatter are axially arranged under the outer vessel 140. It willconsequently be appreciated that in the embodiment of FIG. 7, theturbine 16 must not support the whole weight of the two vapour drums 46,48.

It will be appreciated that in all three arrangements, the low pressurevapour is slightly superheated by contact with one or more walls of thehigh pressure vapour drum 46, which may be advantageous for theefficiency of the low pressure cycle. This superheating-effect is moreimportant for the embodiment of FIG. 7 and may be further amplified byproviding the outer wall of the inner cylinder 46 in FIG. 7 with fins.

FIGS. 9 and 10 show a compact device for electric power generationaccording to an improved ORC, more particularly, to an ORC working withtwo evaporators 12, 14, two regenerators 20, 22 and an induction turbine16, so as illustrated with the circuit of FIG. 1. The container 10 is avertical vapour tight cylinder supported on support feet 150. Theturbine 16 is located inside the vertical cylinder 10, near the top endof the latter. The central axis 74 of the turbine is aligned with thecentral axis of the container 10. Referring back to FIG. 2, it will benoted that the second turbine housing part 100 is fixed with in a sealedmanner to a head-plate 152, which is a part of the upper container wall.The shaft outlet neck axially protrudes out of an opening 153 of thehead-plate 152. Alternatively, the second turbine housing part 100 mayinclude an annular flange (not shown) with which it is fixed in a sealedmanner onto a flange surrounding an axial opening (not shown) in thehead of the container 10. In this case the entire second turbine housingpart 100 is located outside the container 10. A generator 154 isarranged on the top of the vertical cylinder 10 and is coupled to thevertical shaft of the turbine 16. It will be appreciated that with thisarrangement, the bearing arrangement 68 of the turbine shaft 66 islocated completely outside the container 10, which greatly facilitatesthe design of its lubrication system, but also its maintenance.

The high pressure vapour drum 46 and the low pressure vapour drum 48 arearranged axially directly under the turbine 16. Both vapour drums 46, 48are advantageously connected to the first and second tubular vapourinlet connection 82, 84 of the turbine 16 as described e.g. withreference to FIG. 5 or 6 and FIG. 8. The first evaporator 12 and thesecond evaporator 14 are arranged axially directly under the two vapourdrums 46, 48, which can be vertically supported by the two evaporators12, 14, as described with reference to FIG. 8. These two evaporators 12,14 are preferably enclosed in a separate cylindrical compartment 156.The first and second regenerator 20, 22 are arranged annularly aroundthe two vapour drums 46, 48, wherein the second regenerator 22 isarranged directly under the first regenerator 20. The condenser 18 isarranged annularly around the two evaporators 12, 14. The bottom part ofthe vertical cylinder 10 forms a condensate collector 158.

The turbine 16, which is preferably conceived substantially as describedhereinbefore, radially discharges the expanded vapour through the statorexhaust ring 56 ₄ directly into the upper part of the vertical cylinder10. An annular deflector (not shown) may be used to deflect the radiallydischarged vapour axially downwards. This annular deflector may beincorporated into the turbine 16 or be installed as a separate elementinto the container 10. The expanded vapour then passes downwards throughthe first and second regenerator 20, 22, to be finally condensed in thecondenser 18. The condensate is collected in the condensate collector158 at the bottom of the vertical cylinder 10.

The pipe connections 30, 30′, 32, 32′, 34, 34′, 36 and 38 shown in FIG.9 correspond to the inlet/outlet ports with the same reference numbersshown in FIG. 1.

FIG. 10 is a horizontal cross-section of the device shown in FIG. 9.This FIG. 10 shows that the annular heat-exchangers 18, 20, 22 do notoccupy the whole annular space around the separate cylindricalcompartment 156 in which the evaporators 12, 14 are arranged. The freespace, here an angular segment of about 40°, is used for arrangingtherein piping and auxiliary equipment, which is only schematicallyrepresented in FIG. 10 and identified therein with reference number 160.

FIG. 11 shows an alternative embodiment with an air-cooled condenser 170installed outside the container 10, which still contains the evaporators12, 14, the regenerators 20, 22, the vapour drums 46, 48, and theturbine 16, which are advantageously arranged in this container 10 asdescribed hereinbefore with reference to FIG. 9. The bottom half of thecontainer 10, which was occupied by the condenser 18 in the embodimentof FIG. 9, is now empty and connected via a large diameter pipe 172 tothe air-cooled condenser 170. The latter includes a central chimney 174with a closed end 176, which is connected to at least one upper vapourcollector 178. From this upper vapour collector 178 the vapour streamsthrough at least one air-cooled condensing heat exchanger 180, whichcondenses the vapour. The condensate is collected in at least one lowercondensate collector 182 and evacuated back into the condensatecollector 158 in the container 10 through a condensate line 184.Condensate that is already formed in the central chimney 174 flows backinto the condensate collector 158 in the container 10 through the largediameter pipe 172. Reference number 186 identifies a fan for creating anair flow 188 through the condensing heat exchanger(s) 180 and along theouter wall of the chimney 174, which may be equipped with cooling finstoo.

Reference signs list  10 container  12 first evaporator  14 secondevaporator  16 turbine  18 condenser  20 first regenerator  22 secondregenerator  24 condensate pump  26 electrical generator  30 first heatcarrier fluid inlet port of 12  30′ second heat carrier fluid inlet portof 12  32 first heat carrier fluid inlet port of 12  32′ second heatcarrier fluid inlet port of 14  34 cooling fluid outlet port of 18  34′cooling fluid outlet port of 18  36 condensate outlet port  38 firstcondensate inlet port  40 second condensate inlet port  42 external heattransfer circuit in which circulates a heat carrier fluid  44 externalconnection conduit  45 bypass-valve  46 high pressure vapour drum  48low pressure vapour drum  50 external cooling circuit of 18  52 firstvalve (connected to 38)  54 second valve (connected to 40)  56₁, firststator ring,  56₂, second stator ring,  56₃ third stator ring  56₄stator exhaust ring (58)  58₁, curved stator blades (58) of 56₁  58₂,curved stator blades (58) of 56₂  58₃ curved stator blades (58) of 56₃ 58₄ stator exhaust blades  60₁, first rotor ring,  60₂, second rotorring,  60₃ third rotor ring  62₁, curved rotor blades of 60₁  62₂,curved rotor blades of 60₂  62₃ curved rotor blades of 60₃  64 rotordisk  66 turbine shaft  68 bearing  70 sealing device  72 shaft outletneck  74 central axis of 16  75 nut  76 screws for rotor rings  78screws for stator rings (56)  80 first turbine housing part (80)  82first tubular vapour inlet connection  84 second tubular vapour inletconnection  86 annular space (between 82 and 84)  88 first ring-shapedflange (on 82)  90 second ring-shaped flange (on 84)  92 perforated ringzone  94 through-holes in 92  96 end-cap  98 vapour inlet deflectionsurface 100 second turbine housing part (100) 102₁, annular shoulder on56₁, 56₂, 102₂, 56₃ 102₃ 104₁, annular outer rim on 60₁, 60₂, 104₂, 60₃104₃ 106 labyrinth joint 108₁, annular shoulder on 60₁, 60₂ 108₂ 110₂,annular outer rim on 56₂, 56₃ 110₃ 112 labyrinth joint 114 ring-shapednozzle 116 annular concave surface defined by 60₂ 118 annular convexsurface defined by 56₃ 120 cylindrical external wall 122 cylindricalinternal wall 124 high pressure vapour inlet pipe 126 low pressurevapour inlet pipe 130 annular space 132 support flange 134 throughopenings in 132 136 inlet compartment 140 outer vessel 142 verticalsupport means 150 support feet 154 generator 156 separate cylindricalcompartment 158 condensate collector 160 piping and auxiliary equipment170 air-cooled condenser 172 large diameter pipe 174 central chimney 176closed end of 174 178 upper vapour collector 180 condensing heatexchanger 182 lower condensate collector 184 condensate line 186 fan 188air flow

1. A device for power generation according to a Rankine cycle, inparticular according to an organic Rankine cycle (ORC), comprising: aturbine (16) for expanding a vapour of a working fluid; and at least oneheat exchanger (18, 20, 22) through which the expanded vapour has toflow; and a vapour tight container (10) containing said turbine (16) andsaid at least one heat exchanger (18, 20, 22), wherein said turbine (16)has a shaft (66) that is led in a sealed manner out of said container(10) and discharges the expanded vapour directly into said vapour tightcontainer (10), in which the expanded vapour flows through said at leastone heat exchanger (18, 20, 22); characterized in that said turbine (16)is a radial-outward-flow type turbine having: an axial vapour inlet port(82) arranged opposite said shaft and located inside the container (10);and a stator exhaust ring (56 ₄) with stator exhaust blades (58 ₄)defining peripheral vapour exhaust openings for discharging the expandedvapour directly into said vapour tight container (10).
 2. The device asclaimed in claim 1, wherein: said container (10) has the form of avertical cylinder with a top end and a bottom end; said turbine (16) iscentred in said top end of said container (10); and said at least oneheat exchanger (18, 20, 22) is located below said turbine.
 3. The deviceas claimed in claim 1, wherein: said turbine (16) is aradial-outward-flow type multi-stage turbine with vapour induction in atleast one intermediary stage, with an annular vapour inlet port (84)surrounding said axial vapour inlet port (82), said annular vapour inletport (84) being arranged in said turbine (16) so as to annularly induce,in an intermediary stage of said turbine (16), a vapour stream from asecond evaporator (14) into an already partially expanded vapour streamfrom a first evaporator (12).
 4. The device as claimed in claim 1,including a first evaporator (12) and, optionally, a second evaporator(12), wherein: said first evaporator (12) and, if present, said secondevaporator (14) are arranged in said container (10), axially below saidaxial vapour inlet port (82) of said turbine (16); and said at least oneheat exchanger (18, 20, 22) is arranged annularly around said firstevaporator (12) and, if said second evaporator (14) is present,annularly around said first and second evaporator (14).
 5. The device asclaimed in claim 1, further comprising: a first vapour drum (46) that islocated in axial extension of said axial vapour inlet port (82) anddirectly connected to the latter without any intermediate piping; and ifsaid turbine is a multi-stage turbine with vapour induction in anintermediary stage, a second vapour drum that is located in axialextension of said annular vapour inlet port (84) and directly connectedto the latter without any intermediate piping, wherein said secondvapour drum (48) is a compartment inside said first vapour drum (46), orsaid first vapour drum (46) is a compartment inside said second vapourdrum (48).
 6. The device as claimed in claim 5, wherein: said axialvapour inlet port is formed by a first tubular vapour inlet connection(82), which is engaged in a sliding and sealed manner by said firstvapour drum (46); and said annular vapour inlet port, if present, isformed by a second tubular vapour inlet connection (84) surrounding saidfirst tubular vapour inlet connection; said second tubular vapour inletconnection is engaged in a sliding and sealed manner by said secondvapour drum (48), and, if said first evaporator (12) and secondevaporator (14) are arranged axially below said axial vapour inlet port(82) of said turbine (16), said first vapour drum (46) and/or saidsecond vapour drum (48) are supported by said first evaporator (12)and/or second evaporator (14) or by a support structure associated withsaid first evaporator (12) and/or second evaporator (14).
 7. The deviceas claimed in claim 1, said at least one heat exchanger (18, 20, 22)includes: a first regenerator (20) that is arranged in said container(10) so that the exhaust vapour of said turbine (16) flows directlythrough it, said first regenerator (20) being connected to a fluid inletport of a first evaporator (12), so as to reheat said fluid with heatextracted from the exhaust vapour flowing through said first regenerator(20); and optionally, a second regenerator (22) that is arranged in saidcontainer (10) so that the vapour having crossed said first regenerator(20) flows through it, said second regenerator (22) being connected to afluid inlet port of a second evaporator (14), so as to reheat said fluidwith heat extracted from the vapour flowing through said secondregenerator (22); and/or a condenser (18) in which said expanded vapouris condensed; wherein, if present, said first regenerator (20), saidsecond generator (22) and said condenser (18) are arranged below saidturbine (16), vertically one above the other.
 8. The device as claimedin claim 1, further including: a first evaporator (12) connected to anaxial vapour inlet port (82) of said turbine (16); a second evaporator(14) working at a lower evaporation pressure than said first evaporator(12) and connected to an annular vapour inlet port (84) of said turbine(16) for inducing lower pressure vapour into an intermediary stage ofsaid turbine; for said first evaporator (12), a first heat carrier fluidinlet port (30) and a first heat carrier fluid outlet port; for saidsecond evaporator (14), a second heat carrier fluid inlet port (32) anda second heat carrier fluid outlet port; a connection pipe (44)connecting said first heat carrier fluid outlet port to said second heatcarrier fluid inlet port (32); and optionally, a bypass-valve (45)connected between said second heat carrier fluid inlet port (32) andsaid second heat carrier fluid outlet port, for adjusting the flow rateof the heat carrier fluid in said second evaporator (14).
 9. The deviceas claimed in claim 8, wherein: said at least one heat exchanger (18,20, 22) includes a condenser (18); a condensate collector (158) isarranged under said condenser (18) in said container (10); a condensateoutlet port (36) is connected to said condensate collector; a firstcondensate inlet (38) is connected either directly or through a firstregenerator (20) to a first evaporator (12); a second condensate inlet(40) is connected either directly or through a second regenerator (22)to a second evaporator (14); and a condensate pump (24) is connectedwith its suction side to said condensate collector (36), and with itspressure side via a first valve (52) to said first condensate inlet (38)and via a second valve (54) to said second condensate inlet (40). 10.The device as claimed in claim 1, including: an air-cooled condenser(170) arranged outside said container (10) and connected to saidcontainer (10) by means of a large diameter pipe (172); wherein said atleast one heat exchanger (18, 20, 22) includes at least one regenerator(20, 22) arranged in said container (10) so that the expanded vapourflows through it before being channelled through said large diameterpipe (172) into said air-cooled condenser (170).
 11. The device asclaimed in claim 1, wherein said turbine (16) comprises: a substantiallyplate-shaped first turbine housing part (80) including said axial vapourinlet port (82); a set of stator rings (56) with stator blades (58),said stator rings (56) having increasing diameters and being fixed withscrews onto said first turbine housing part (80); said stator exhaustring (56 ₄) radially surrounding the stator ring with the biggestdiameter and being fixed with screws onto said first turbine housingpart (80), said stator exhaust blades defining said vapour exhaustopenings for discharging the expanded vapour into said container (10); asubstantially plate-shaped second turbine housing part (100) including ashaft outlet neck (72); said second turbine housing part (100) beingfixed with screws onto said stator exhaust ring (58); a turbine (16)shaft rotatably supported within said shaft outlet neck (72); a rotordisk (64) supported in a cantilever manner by said turbine (16) shaftbetween said first turbine housing part (80) and said second turbinehousing part (100); for each stator ring (56), a rotor ring (60) withrotor blades (62), said rotor ring (60) radially surrounding thecorresponding stator ring (56) and being fixed with screws onto saidrotor disk (64).
 12. The device as claimed in claim 11, wherein: saidturbine (16) includes an annular vapour inlet port (84) formed in saidfirst turbine housing part (80) as a ring-zone (92) with through-holes(94), said ring-zone (92) separating a first ring-shaped flange (88),which supports a first set of stator rings (56), from a secondring-shaped flange (90), which supports a second set of stator rings(56).
 13. The device as claimed in claim 1, wherein said turbine (16)comprises: a first turbine housing part (80) including said axial vapourinlet port (82); a set of stator rings (56) with stator blades (58)supported by said first turbine housing part (80); a turbine (16) shaftsupporting in a cantilever manner a rotor disk; for each stator ring(56), a rotor ring (60) with rotor blades (62), said rotor ring (60)radially surrounding the corresponding stator ring (56) and beingsupported by said rotor disk (64); an annular vapour inlet port (84)formed in said first turbine housing part (80) as a ring-zone (92) withthrough-holes (94); wherein said through-holes (94) open onto an outerrim (104 ₂) of one of said rotor rings (60), said outer rim (104 ₂)having a width decreasing towards its periphery, and forming an annular,preferably concave, surface, which defines with an annular, preferablyconvex, surface on the next stator ring (56), a ring-shaped convergingnozzle (114), for annularly inducing, into said next stator ring (56), avapour stream from said through-holes (94) into a vapour stream flowingthrough the preceding rotor ring (60).
 14. The device as claimed inclaim 1, wherein said first turbine housing part (80) supports anend-cap (96), which forms a vapour inlet deflection surface (98)opposite said axial vapour inlet port (82), said vapour inlet deflectionsurface (98) being a revolution surface centred on said central axis(74) of the turbine (16), wherein a first stator ring (56 ₁) isintegrated into said end-cap (96).
 15. The device as claimed in claim 1,wherein said second turbine housing part (100) is mounted in a sealedmanner in an opening of said container (10), so that a shaft outlet neck(72) of said second turbine housing part (100) is located outside saidcontainer (10), and said turbine (16) further includes: rolling contactbearings in said shaft outlet neck (72) for supporting and locating saidturbine (16) shaft therein; and a shaft sealing device located adjacentto said rolling contact bearings, so that said rolling contact bearingsare sealed from the vapour in the turbine (16).